Screening type peripheral discharge mill



May 18, 1965 A. c. DAMAN 3,184,171

SCREENING TYPE PERIPHERAL DISCHARGE MILL Filed June 18, 1962 4 Sheets-Sheet 1 MIMI MUUMMIIUU [IUBUOBUM INVWTOR. Arthur C. Damon ATTORNEYS May 18, 1965 Filed June 18, l 62 A. c. DAMAN SCREENING TYPE PERIPHERAL DISCHARGE MILL 4 Sheets-Sheet 2 "'3 x l ATTORNEYS May 18, 1965 A. c. DAMAN 3,184,171

SCREENING TYPE PERIPHERAL DISCHARGE MILL Filed June 18, 1962 4 Sheets-Sheet 3 INVENTOR. Arthur C. Daman ATTORNEYS May 18, 1965 A. c. DAMAN 3,134,171

SCREENING TYPE PERIPHERAL DISCHARGE MILL Filed June 18, 1962 4 Sheets-Sheet 4 INVENTOR. Arthur C. Daman am i'M ATTORNEYS United States Patent Ofi 3,l8d,l7l Patented May l8, 2%65 ice 3,184,171 SCREENING TYPE PERQI-ERAL DISQHARGE MlLL Arthur Chester Daman, Denver, Colo, assignor to Denver Equipment Qompany, Denver, (3010., a corporation of Colorado Filed June 18, 1962, Ser. No. 203,052 8 Claims. (Cl. 241-83) This invention relates to grinding mills and more particularly relates to screening type, peripheral discharge mills.

Mills of the aforesaid type, particularly those classed as one pass mills, have many industrial uses in both wet and dry grinding operations. They have the advantage of avoiding serious overgrinding as particles reduced to a desired size pass the exterior screening surface and discharge fiom the mill so that there is no substantial retention of undersize in the grinding zone. They have the disadvantage of retaining all oversize until it reduces to the required degree, and frequently there is such an accumulation of oversize in the mill or in areas of the mill that discharge capacity is reduced to an undesirable degree.

In addition, such mills do not have provision for effective sorting and distribution of oversize within the grinding zone with the result that too much of the total charge may be contained in one area of the mill whereas another area may have a deficiency and operate inefficiently. This condition leads to inefiicient grinding, overload on bearings, erratic circuit operation, and in some instances complete shutdown. It also causes excessive wear on some wear surfaces with resulting interference with maintenance and repair schedules.

Accordingly, it is an object of my invention to provide a simple, durable and eificient screening type peripheral discharge mill incorporating an induced discharge action in association with its screening structure.

Another object of this invention is to provide a sluicing action in association with the screening separation of a peripheral discharge mill which action also is utilized as a circulating control for distribution of material in the grinding zone of the mill.

A further object of my invention is the provision of a novel type of roller for the grinding zone of such a mill which functions as a feed distributor in addition to providing the requisite crushing or grinding action in the grinding zone.

Still another object of my invention is to provide a simple, durable and efiicient screening type, peripheral discharge mill having controlled sorting and distribution of circulating oversize in the mill.

Other objects reside in novel details of construction and novel combinations and arrangements of parts, all of which will be disclosed in detail in the course of the following description.

The practice of my invention will be described with reference to the accompanying drawings illustrating typical structural embodiments. In the drawings, in the several views of which like parts bear similar reference numerals,

FIG. 1 is a side elevation of a grinding mill embodying features of my invention and partially broken to show the arrangement of components of the screening structure;

FIG. 2 is a fragmentary vertical section through the mill of FIG. 1 intermediate its ends and drawn to an enlarged scale to show the assembly arrangement of one form of screening structure;

FIG. 3 is a fragmentary vertical section through the longitudinal axis of the mill of FIG. 1 drawn to an enlarged scale to show details of the water distribution arrangement of the assembly;

FIG. 4 is a vertical section, taken along the line 44, FIG. 5, with the spray nozzle position included;

FIG. 5 is a top plan view of the mounting arrangement of a liner section within a mill of the type shown in FIG. 1; and

FIG. 6 is a section taken along the line 66, FIG. 3.

As shown in FIG. 1, a grinding mill embodying features of my invention comprises a hollow drum type portion 12 closed by heads 13a and 13b and having a feed trunnion 14 for introduction of material to be ground. The mill is mounted in suitable bearings 15a and 15b for rotation about a horizontal axis and the bearings are mounted on rigid supporting structure, such as the pedestal type foundations 16 shown in FIG. 1. A suitable motor (not shown) drives a pulley or sheave 17 mounted on a shaft 18 journalled in a plurality of bearings 19. A pinion 20 on shaft 18 meshes with a gear 21 secured on a plate 21x carried by a trunnion extending from head 13!) and rotates the mill at a selected or predetermined speed.

A feeder 22 mounted on trunnion 14 collects and introduces feed material through said trunnion for discharge into the mill. Water or other solution may be delivered into the mill interior for purposes to be described subsequently and a nipple 23 leading to a swivel type distribution valve 24 will be connected to a supply line (not shown) when liquid introduction is utilized. As shown in FIGS. 3 and 6, distribution valve 24 has an inlet sleeve 60 alined with nipple 23 which is stationary during operation, but externally adjustable by loosening bolts si on the supporting structure 62 of nipple 23 to selectively vary the position of a distribution port 63 within a rotating manifold 64 having a plurality of separated chambers 65. Each chamber has an inlet 65a to receive flow from sleeve 60 and each chamber communicates with one of the series of headers 25 by which the water is conducted to the interior of the mill. After a given inlet dSa moves out of register with port 63, water supply to its associated header 25 is terminated until the next cycle of rotation. As shown in FIG. 3, the head 1312 at the trunnion end is a sectional arrangement with the inner and outer portions joined as shown at 26. The adjoining foundation 16 has a separable support portion 16a and when access to the interior is required, the head sections are separated by removal of the bolts 32 and the trunnion 14 and support portion 16a are drawn outwardly. This provides an opening of substantial diameter.

The interior working surface of the mill is formed by a plurality of sectional liners 3d joined as an annular assembly. As shown in FIGS. 3, 4 and 5, each section 39 has flanged end portions 31, apertured as shown at 32 for bolted connection with heads 13a and 13b as shown at 33 for the support of such section within the rnill. Each section has an outwardly extending portion 34 which provides support for an annular perforate plate 35 at the periphery of the drum portion 12 and defines therewith a separation or sorting chamber 36 with the flange or extension 34 acting as partitioning means for separating the chamber -36 from the forward adjoining chamber. The main body portion 37 of each liner section has a series of slotted apertures 38 which widen toward the periphery of the mill so that inner rim of the aperture determines the screen size of the material which will penetrate such apertures. The end of portion 37 opposite flange 34 terminates in spaced relation to the adjoining flange 34 of the next section to define a passage 39 for return of oversize into the interior of the mill.

For many treatments, the annular plate member 35 will be the dual screening unit of the assembly and the oblong openings 40 therein will determine the size of the finished product discharge which passes into a hopper 41 shown in dash lines in FIG. 1, or to any other suitable collecting and conveying means (not shown). Theopenings so preferably are formed so that the maximum discharge capacity is provided when they move into a vertical position. The openings 33 in the liner sections are substantially larger than the openings 40 and pass a considerable amount which is oversize at openings 40. By so doing, finished product is removed from the grinding zone in the mill interior as it is formed and is sorted from associated material in chambers 36 to pass through openings 4% as a discharge product. Oversize in chambers 36 is returned to the grinding zone through passages 39 by the tumbling action of the mill when dry grinding is practiced.

However, the mill illustrated is particularly suited for wet grinding operations and in such operations wash liquid introduction may be included. Nipple 23 is connected with a source of supply as previously explained and the swivel valve 24 is set to pass wash liquid in a selected volume into the headers 25 for discharge through spray heads 42 extending substantially across the lengthwise extent of the sorting chambers 36 at their advance or forward ends. The valve setting provides on-and-otf operation with liquid discharge while a given chamber 36 is in a downward discharge position and how out off while such chamber passes through the remaining part of its rotary cycle. The liquid discharge has a sluicing elfect on the solids content of the chamber inducing rapid discharge of finished product through the openings 40 and sweeping oversize to the trailing end of the chamber where it discharges through the passage 39 as soon as the liner section is elevated in the rotation of the mill to permit return flow through said passage.

When the finished product is required to be in a fine sized range, the plate 35 may be covered with a fine screen member 45, as shown in FIG. 1, preferably formed as a strip having both of its ends upset and held by hook bolts 46 extending through comp-anion lugs 47 and 47x secured on plate 35 and a nut 48 hearing against an adjoining lug is used to draw the hook bolt and tauten screen 45. The mesh of screen 45 determines the particle size of the finished product in this arrangement and oversize entering openings 40 which will not pass the screen spills or is sluiced out during the elevating action to move through passage 39 and into the grinding zone.

As shown in FIG. 2, a sectional type of roll may be utilized to provide the crushing action in the grinding zone although grinding balls, rod-s or the like may be used if preferred. The roll assembly 50 shown in FIGS. 2 and 3, comprises three sections in end-abutting relation to form :an essential integral structure. The sections are hollow and collectively provide a central hollow portion 51 for passage of material throughout its length. Companion grooves extend from the passage '51 to the periphery of each section and in facing relation provide a series of substantially radial passages 52 for discharge of contained material from the passage 51. The roller assembly may be of any suitable size, and as illustrated in FIG. 2 is of a diameter permitting its insertion and removal through the central access opening at 26 after removal of the trunnion and connected head section as previously described. The roller is caused to rotate by the tumbling action of the mill and crushes oversize deposited on the inner surfaces of liners 39 and in the rolling or compacting action forces undersize through the openings 38 into chambers 36. Material entering the central passage 51 is moved into the discharge passages 52 during rotation of roller 50 and thus is discharged and brought against the surfaces of the liner sections for additional compaction and crushing by the rolling action.

In order to provide more control of the separation and recirculation of material in the separation chambers 36 and in the oversize return to the mill interior, the liner sections may be provided with a series of ribs or vanes 55 (FIGS. 4 and which are angularly positioned on the liners in a helical pattern to direct the solids and any associated liquid toward the feed end of the mill interior. This arrangement tends to confine the slu-icing action so as to attain a more rapid penetration of the openings 40 by the liquid and fine solids while directing the oversize reject of the openings 40 to the passage '39 for return in separated flows to the interior of the mill at spaced points along its length. In some treatments, only the sluicing action will be required in obtaining the induced screening separation and circulating control and it will be understood that the vanes 55 will not be formed on the liners when circulating control is not required.

While inclusion of a roller such as roller 51 is desirable for many treatments, it will be understood that other grinding media may be used, such as balls, rods or the like (not shown). The oblong shape of the passages 38 permits passage of a substantial quantity of material in sizes substantially larger than the openings 4% of the extcrior screening member and thus circulates a substantial part of the material approaching the desired degree of size reduction. The openings 38 also effectively separate the grinding media from contact with the screening surfaces of the exterior member 35 and thus all wear resulting from movement of the grinding media is confined within the liner assembly. The provision of an annular liner formed of a plurality of sections and secured only at its ends against the heads of the mill permits quick and easy removal and replacement of a broken or damaged liner section through the central access opening. Consequently, damage and repair can be undertaken when necessary without dismantling the entire mill and with only a brief interruption in the operating schedule.

The combination of the mill rotation and the spray heads 4-2 at the upstream end of the separating chambers 36 provides a substantial sluicing action toward the downstream end of the chamber. In such movement, the liquid tends to discharge by gravity through the openings 40 and the interstices of the fine screen 45 is included in the assembly, and in so doing entrains associated fines. This sluicing action is only required in the ascending pass of the cycle and the valve 24 provides on and off control so that the water or other solution is only supplied as required. In addition to providing the on and off control, the valve 24 also may be regulated to provide a variable flow of wash liquid to adjust for varying conditions within the mill during continuous operation. When the fine screen 45 is included, oversize penetrating the passages 40 will be returned to the separating chamber 36 as it ascends above the center of the mill and in the position in which it will discharge by gravity, the passage 39 is so disposed that such material returns promptly to the interior of the mill.

The oblong shaping of the openings 38 in the liner sections and the enlargement of the passage from the inner surface to the outer surface insures that any particle penetrating the inner end of the passage will not become lodged therein but passes readily therethrough due to the enlarging space provided by such an arrangement. The openings 4% in the outer screening member 35 also are oblong and enlarge from the inner face to the outer face and thereby avoid blockage which other- Wise might result from particles lodging in such openings. This arrangement provides a rapid discharge of all sizes which will pass the outermost screening opening and most oversize is moved directly to the passage 39 for return to the mill. Consequently, the maximum available screening surface is maintained at substantially optimum capacity throughout the separating cycle and provides a much higher rate of discharge than is usual in a peripheral discharge mill.

Changes and modifications may be availed of within the spirit and scope of the invention as set forth in the hereunto appended claims.

I claim:

1. A grinding mill comprising a cylindrical drum mounted on a supporting structure for rotation about a substantially horizontal axis and having a head closing each of its ends, a feed trunnion extending into one said end, a plurality of segmental liners assembled to form a perforate, annular structure adjacent but spaced from the periphery of the drum and fitted between the heads, a second perforate, annular member exteriorly of the liner structure having screening portions in spaced relation thereto, partitioning means on the liners having a portion extending into the space between the annular members and defining therewith a plurality of separation chambers in circumferential arrangement about the drum, there being a passage at the trailing end of each chamber for conducting oversize reject to the interior of the drum, means in the forward end of each chamber for discharging a sluicing flow throughout the chamber, means for intermittently supplying sluicing liquid to the discharge means, the openings in the outer annular mem being of a dimension to pass a predetermined, maximumsize material as the product discharge of the mill and to reject oversize, the openings in the liner members being larger than the openings in the outer annular member, and means for rotating said drum.

2. A grinding mill comprising a cylindrical drum mounted on a supporting structure for rotation about a substantially horizontal axis and having a head closing each of its ends, a feed trunnion extending into one said end, a plurality of segmental liners assembled to form a perforate, annular structure adjacent but spaced from the periphery of the drum and fitted between the heads, a second perforate, annular member exteriorly of the liner structure having screening portions in spaced relation thereto, partitioning means on the liners having a portion extending into the space bet-ween the annular members and defining therewith a plurality of separation chambers in circumferential arrangement about the drum, there being a passage at the trailing end of each chamber for conducting oversize reject to the interior of the drum, valve controlled means for discharging a variable sluicing flow of liquid into the forward end and through each chamber, means for supplying sluicing liquid to said valve controlled means, the openings in the outer annular member being of a dimension to pass a predetermined, maximum-size material as the product discharge of the mill and to reject oversize, the openings in the liner members being larger than the openings in the outer annular member, and means for rotating said drum.

3. A grinding mill comprising a cylindrical drum mounted on a supporting structurue for rotation about a substantially horizontal axis and having a head closing each of its ends, a feed trunnion extending into one said end, a plurality of segmental liners assembled to form a perforate, annular structure adjacent but spaced from the periphery of the drum and fitted between the heads, a second perforate, annular member exteriorly of the liner structure having screening portions in spaced relation thereto, partitioning means on the liners having a portion extending into the space between the annular members and defining therewith a plurality of separation chambers in circumferential arrangement about the drum, there being a passage at the trailing end of each chamber for conducting oversize reject to the interior of the drum, means in the forward end of each chamber for discharging sluicing fiow throughout the chamber, means for supplying sluicing liquid to the discharge means, means on the outer surface of the liners for directing material through said passage into the mill interior toward the feed end thereof, the openings in the outer annular memher being of a dimension to pass a predetermined, maximum-size material as the product discharge of the mill and to reject oversize, the openings in the liners being larger than the openings in the outer annular member, and means for rotating said drum.

4. A grinding mill comprising a cylindrical drum mounted on a supporting structure for rotation about a substantially horizontal axis and having a head closing each of its ends, a feed trunnion extending into one said end, a plurality of segmental liners assembled to form a perforate, annular structure adjacent but spaced from the periphery of the drum and fitted between the heads, a plurality of segmental members assembled to form a second perforate, annular member exteriorly of the liner structure having screening portions in spaced relation thereto, partitioning means on the liners having portions extending into the space between the annular members and defining therewith a plurality of separation chambers in circumferential arrangement about the drum, there being a passage at the trailing end of each chamber for conducting oversize reject to the interior of the drum, means in the forward end of each chamber for discharg ing sluicing flow throughout the chamber, means for supplying sluicing liquid to the discharge means, helical ribs on the outer surface of the liners for directing oversize material in separated flows through said passage into the mill interior toward the feed end thereof, the openings in the outer annular member being of a dimension to pass a predetermined, maximum-size material as the product discharge of the mill and to reject oversize, the openings in the liners being larger than the openings in the outer annular member, and means for rotating said drum.

5. A grinding mill comprising a cylindrical drum mounted on a supporting structure for rotation about a substantially horizontal axis and having a head closing each of its ends, a feed trunnion extending into one said end, a plurality of segmental liners assembled to form a perforate, annular structure adjacent but spaced from the periphery of the drum and fitted between the heads, the perforations of said liners comprising elongated slots, a second perforate, annular member exteriorly of the liner structure having screening portions in spaced relation thereto, partitioning means on the liners having portions extending into the space between the annular members and defining therewith a plurality of separation chambers in circumferential arrangement about the drum, there being a passage at the trailing end of each chamber for conducting oversize reject to the interior of the drum, means in the forward end of each chamber for discharging sluicing flow throughout the chamber, means for supplying sluicing liquid to the discharge means, the openings in the outer annular member being of a dimension to pass a predetermined, maximum-size material as the product discharge of the mill and to reject oversize and being smaller than said elongated slots, and means for rotating said drum.

6. A grinding mill comprising a cylindrical drum mounted on a supporting structure for rotation about a substantially horizontal axis and having a head closing each of its ends, a feed trunnion extending into one said end, a plurality of segmental liners assembled to form a perforate, annular structure adjacent but spaced from the periphery of the drum and fitted between the heads, the perforations of said liners comprising oblong slots, a second perforate, annular member exteriorly of the liner structure having screening portions in spaced relation thereto, partitioning means on the liners having portions extending into the space between the annular members and defining therewith a plurality of separation chambers in circumferential arrangement about the drum, there being a passage at the trailing end of each chamber for conducting oversize reject to the interior of the drum, means in the forward end of each chamber for discharging sluicing flow throughout the chamber, means for supplying sluicing liquid to the discharge means, the openings in the outer annular member being of a dimension to pass predetermined, maximum-size material as the product discharge of the mill and to reject oversize and being smaller than said oblong slots, and means for rotating said drum.

7. A grinding mill comprising a cylindrical drum mounted on a supporting structure for rotation about a substantially horizontal axis and having a head closing each of its ends, a feed trunnion extending into one said end, a plurality of segmental liners assembled to form a perforate, annular structure adjacent but spaced from the periphery of the drum and fitted between the heads, a second perforate, annular member exteriorly of the liner structure having screening portions in spaced relation thereto, partitioning means on the liners having a portion extending into the space between the annular members and defining therewith a plurality of separation chambers in circumferential arrangement about the drum, there being a passage at the trailing end of each chamber for conducting oversize reject to the interior of the drum, means in the forward end of each chamber for discharging a sluicing flow of liquid throughout the chamber, means for supplying sluicing liquid to the discharge means during a selected interval in each cycle of revolution, the openings in the outer annular member being of a dimension to pass a predetermined, maximum-size material as the product discharge of the mill and to reject oversize, the openings in the liner members being larger than the openings in the outer annular member, and means for rotating said drum. 7

8. A grinding mill comprising a cylindrical drum mounted on a supporting structure for rotation about a substantially horizontal axis and having a head closing each of its ends, a feed trunnion extending into one said end, a plurality of segmental liners assembled to form a perforate, annular strucuture adjacent but spaced from the periphery of the drum and fitted between the heads, a second perforate, annular member exteriorly of the liner structure having screening portions in spaced relation thereto, partitioning means on the liners having a portion 30 extending into the space between the annular members and defining therewith a plurality of separation chambers in circumferential arrangement about the drum, there being a passage at the trailing end of each chamber for conducting oversize reject to the interior of the drum, means in the forward end of each chamber for discharging a sluicing flow of liquid throughout the chamber, means including a swivel valve for supplying sluicing liquid to each of the discharge means during a selected interval in each cycle of revolution, the openings in the outer annular member being of a dimension to pass a predetermined, maximum-size material as the product discharge of the mill and to reject oversize, the openings in the liner members being larger than the openings in the outer annular member, and means for rotating said drum.

References Cited by the Examiner UNITED STATES PATENTS 64,416 5/67 Hart 241l76X 248,122 10/81 Tustin 24l172 X 288,745 11/83 Tustin 241172 X 647,336 4/00 Sulman 241-171 X 1,441,584 1/23 Isbell 241-91 X 1,477,376 12/23 Moyle 241171 X 2,126,406 8/38 Minnick 24ll79 X FOREIGN PATENTS 408,582 4/34 Great Britain. 786,219 11/57 Great Britain.

I. SPENCER OVERHOLSER, Primary Examiner.

EVERETTE W. KIRBY, Examiner. 

1. A GRINDING MILL COMPRISING A CYLINDRICAL DRUM MOUNTED ON A SUPPORTING STRUCTURE FOR ROTATION ABOUT A SUBSTANTIALLY HORIZONTAL AXIS AND HAVING A HEAD CLOSING EACH OF ITS ENDS, A FEED TRUNNION EXTENDING INTO ONE SAID END, PLURALITY OF SEGMENTAL LINERS ASSEMBLED TO FORM A PERFORATE, ANNULAR STRUCTURE ADJACENT BUT SPACED FROM THE PERIPHERY OF THE DRUM AND FITTED BETWEEN THE HEADS, A SECOND PERFORATE, ANNULAR MEMBER EXTERIORLY OF THE LINER STRUCTURE HAVING SCREENING PORTIONS IN SPACED RELATION THERETO, PARTITIONING MEANS ON THE LINERS HAVING A PORTION EXTENDING INTO THE SPACE BETWEEN THE ANNULAR MEMBERS AND DEFINING THEREWITH A PLURALITY OF SEPARATION CHAMBERS IN CIRCUMFERENTIAL ARRANGEMENT ABOUT THE DRUM, THERE BEING A PASSAGE AT THE TRAILING END OF EACH CHAMBER FOR CONDUCTING OVERSIZE REJECT TO THE INTERIOR OF THE DRUM, MEANS IN THE FORWARD END OF EACH CHAMBER FOR DISCHARGING A SLUICING FLOW THROUGHOUT THE CHAMBER, MEANS FOR INTERMITTENTLY SUPPLYING SLUICING LIQUID TO THE DISCHARGE MEANS, THE OPENINGS IN THE OUTER ANNULAR MEMBER BEING OF A DIMENSION TO PASS A PREDETERMINEDM, MAXIMUMSIZE MATERIAL AS THE PRODUCT DISCHARGE OF THE MILL AND TO REJECT OVERSIZE, THE OPENINGS IN THE LINER MEMBERS BEING LARGER THAN THE OPENINGS IN THE OUTER ANNULAR MEMBER, AND MEANS FOR ROTATING SAID DRUM. 